Impact-resistant pad and method of manufacturing

ABSTRACT

Impact-resistant pads, methods of manufacturing impact-resistant pads, and protective apparatuses are disclosed. An impact-resistant pad includes a spacer fabric, a fluid permeated within the spacer fabric, and a containment layer encapsulating the spacer fabric and the fluid. The fluid has a viscosity dependent on a force applied to the pad. A method for manufacturing the impact-resistant pad is includes cutting a spacer fabric to a desired shape, providing a fluid having a viscosity dependent on a force applied to the pad, permeating the spacer fabric with the fluid, and encapsulating the spacer fabric and the fluid with a containment layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase application of PCT International Application No. PCT/US2012/054716, filed Sep. 12, 2012, and claims priority to provisional application No. 61/534,549, filed Sep. 14, 2011, which applications are incorporated herein by reference in their entireties and for all purposes.

FIELD OF THE INVENTION

The invention relates generally to the field of protective garments, and more particularly, to impact-resistant pads and equipment.

BACKGROUND OF THE INVENTION

Conventionally, participants in “contact” sports (e.g., football, rugby) wear pads or other protective garments to cushion the force of impacts that are regularly received during those events. In recent years, the negative health effects of the impacts experienced during such contact sports have been a matter of focus. These negative health effects can be diminished or minimized by effectively cushioning athletes from the forces of impacts. Accordingly, improved structures, such as impact-resistant pads, are desired to lessen the impact forces experienced by sport participants.

Conventional impact-resistant pads may be made from neoprene, polyurethane, and/or EVA foams that are provided in order to dissipate mechanical energy imparted during an impact. Other products use impact absorption gels to lessen the force felt during impacts. One such material is Beta gel, a soft silicone material provided by Geltec Corporation, of Tokyo, Japan. Beta gel is similar to known foams inasmuch as it is always soft and does not respond differently in response the magnitude of an impact.

Improved impact-resistant pads are desired that further lessen the force experienced by the wearer during an impact.

SUMMARY OF THE INVENTION

Aspects of the present invention are directed to impact-resistant pads, methods of manufacturing impact-resistant pads, and protective apparatuses.

In accordance with one aspect of the present invention, an impact-resistant pad is disclosed. The impact-resistant pad comprises a spacer fabric, a fluid permeated within the spacer fabric, and a containment layer encapsulating the spacer fabric and the fluid. The fluid has a viscosity dependent on a force applied to the pad.

In accordance with another aspect of the present invention, a method for manufacturing an impact-resistant pad is disclosed. The method comprises cutting a spacer fabric to a desired shape, providing a fluid having a viscosity dependent on a force applied to the pad, permeating the spacer fabric with the fluid, and encapsulating the spacer fabric and the fluid with a containment layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed description when read in connection with the accompanying drawings, with like elements having the same reference numerals. When a plurality of similar elements are present, a single reference numeral may be assigned to the plurality of similar elements with a small letter designation referring to specific elements. When referring to the elements collectively or to a non-specific one or more of the elements, the small letter designation may be dropped. According to common practice, the various features of the drawings are not drawn to scale unless otherwise indicated. To the contrary, the dimensions of the various features may be expanded or reduced for clarity. Included in the drawings are the following figures:

FIG. 1 is a cross-sectional diagram illustrating an exemplary impact-resistant pad in accordance with aspects of the present invention;

FIG. 2 is a cross-sectional diagram illustrating an exemplary protective apparatus in accordance with aspects of the present invention;

FIG. 3 is a flowchart illustrating an exemplary method for manufacturing an impact-resistant pad in accordance with aspects of the present invention;

FIG. 4 is a graph illustrating shear stress vs. viscosity for an exemplary impact-resistant pad of the present invention;

FIG. 5 is a graph illustrating force vs. displacement for another exemplary impact-resistant pads of the present invention;

FIG. 6 is a graph illustrating energy dissipation vs. impact kinetic energy for other exemplary impact-resistant pads of the present invention;

FIG. 7 is a cross-sectional diagram illustrating a conventional impact-resistant pad for use in an American football helmet;

FIG. 8 is a cross-sectional diagram illustrating an exemplary impact-resistant pad for use in an American football helmet in accordance with aspects of the present invention; and

FIGS. 9-13 are graphs illustrating force vs. displacement for an exemplary impact-resistant pad of the present invention;

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the invention described herein relate to an impact-resistant pad that incorporates a fluid having a viscosity which is dependent on applied force (e.g., a shear thickening fluid). As used herein, the term “impact” is intended to encompass any contact that transfers a force from one object to another. Additionally, as used herein, the term “impact-resistant” is intended to encompass any object that partially or fully lessens, diminishes, dissipates, or absorbs the mechanical force of an impact.

The impact-resistant pads disclosed herein are configured to lessen the force of an impact on the pad's user or wearer. This makes them suitable for use by participants in athletic activities, and particularly suitable for participants in traditional “contact” sports, such as American football or rugby, where high-force impacts may be commonly experienced. Although ideal for use as head padding in helmets, the invention is not limited to use in connection with any particular type of helmet, for any particular area of the body, or for any particular sport or activity. Suitable applications for the impact-resistant pads of the present invention will be readily understood by one of ordinary skill in the art from the description herein.

Exemplary embodiments of the present invention described herein employ shear thickening fluids to provide the desired impact-resistance. In general, shear thickening fluids are highly concentrated suspensions of colloidal and/or nanoparticles in a low molecular weight fluid, in which hydroclusters form above a critical stress, resulting in an increase in viscosity. Hydroclusters are transient groupings of particles that are formed when hydrodynamic forces keep particles in close proximity, creating transient clusters of high particle density. These clusters experience higher fluid stress due to the increased local particle density, which enables shear thickening fluids to have superior energy dissipation properties compared to simple fluids and gels. As this non-Newtonian response of the STFs increases with increasing flow rate, these are field-responsive materials, i.e., they exhibit better impact absorbing properties as impact force increases. The field-induced response of STFs is in direct contrast to traditional materials, such as conventional foams, which fail catastrophically when overmatched by an impact threat. The size and volume fraction of particles in the STF formulation, along with the properties of the suspending medium, determines the severity of the thickening response as shear stress increases.

Referring now to the drawings, FIG. 1 illustrates an exemplary impact-resistant pad 100 in accordance with aspects of the present invention. Impact-resistant pad 100 may be usable as part of a protective apparatus worn by a participant during an athletic activity. As a general overview, pad 100 includes a spacer fabric 110, a fluid 120, and a containment layer 130. Additional details of pad 100 are described herein.

Spacer fabric 110 defines a shape and size of pad 100. Spacer fabric 110 has a three-dimensional shape that corresponds to (and defines) the desired shape and size of pad 100. The shape of spacer fabric 110 may be selected based on the desired use of the pad. For example, when pad 100 forms part of a protective apparatus to be worn by a user, spacer fabric 110 may have a shape that conforms to an external periphery of the region of the user's body where the pad will be worn. The shape of spacer fabric 100 may be generated, for example, by compression molding. The ability to mold spacer fabric 100 may allow pad 100 to be custom fit to various anatomical features with complex curvature (e.g., head, shoulders, knees, elbows, chest, back, ribs, hips, etc.).

Spacer fabric 110 is desirably formed from a compressible material. Preferably, spacer fabric 110 is formed from an elastically deformable material, i.e., a material that can be compressed by the force of an impact, and inherently returns to its original shape after the impact force has ceased. In an exemplary embodiment, spacer fabric 110 comprises a polyester material. Suitable fabrics for use as spacer fabric 110 include, for example, Gehring D³ fabrics, provided by Gehring Textiles, Inc., of Garden City, N.Y., USA. Spacer fabric 110 may desirably have a thickness of between 1.5 mm and 15 mm.

Fluid 120 is permeated within spacer fabric 110. Spacer fabric 110 may be soaked in a quantity of fluid 120, such that fluid 120 completely saturates spacer fabric 110. Fluid 120 may further surround, coat, or otherwise cover all or a portion of spacer fabric 110.

Fluid 120 has a viscosity dependent on a force applied to pad 100. Preferable, fluid 120 has a viscosity that increases when an external force is applied to pad 100. Suitable fluids for use as fluid 120 include, for example, non-Newtonian fluids. In an exemplary embodiment, fluid 120 is a shear thickening fluid. As used herein, the term “shear thickening fluid” encompasses all fluids in which a viscosity of the fluid increases in response to a shear stress or force.

Shear thickening fluid used as fluid 120 may have a viscosity that is dependent on the magnitude of deformation, such that it thickens to a greater extent during greater impacts. The responsive nature of the fluid desirably allows it to be soft and flexible before an impact, while becoming stronger and more rigid during impact, after which it relaxes and becomes soft again. As compared to gels, the shear thickening fluid used in this invention may be more suitable for inclusion in pads having three dimensional shapes, by virtue of being a fluid (which can take the shape of any container), as opposed to a gel which must be formed into sheets and cut into custom shapes.

In a more preferred embodiment, the shear thickening fluid comprises silica nanoparticles and/or polyethylene glycol. Suitable shear thickening fluids for use with the present invention may be prepared by dispersing 55, 58, and 61 percent by weight of silica nanoparticles in 200 MW polyethylene glycol (PEG). The silica nanoparticles may be NANOSIL® silica particles, provided by Bokwang Chemical Co., Ltd., of Chungcheongnam-do, South Korea.

Containment layer 130 encapsulates spacer fabric 110 and fluid 120. Containment layer 130 desirably encapsulates fluid 120 such that no fluid 120 may leak from pad 100. Containment layer 130 is desirably a thin coating of material in order to prevent pad 100 from being overly thick. In an exemplary embodiment, containment layer 130 comprises a polyolefin material having a thickness of between 0.5-1.0 mm. Suitable materials for use as containment layer 130 include, for example, ENGAGE® 8200 polyolefin elastomer, provided by Dow Chemical Co., of Midland, Mich., USA. However, it will be understood that any materials with sufficient toughness and chemical resistance to penetration by the fluid will be acceptable. For example, in an exemplary system in which the fluid comprises polyethylene glycol (PEG), other suitable PEG-resistant encapsulating materials may include polyurethane film, silicone rubber, VITON® rubber (available from E.I. DuPont de Nemours & Co., of Wilmington, Del.), and/or latex.

As described above, pad 100 may be usable as part of a protective apparatus worn by a participant in an athletic activity. Accordingly, it may be desirable that pad 100 be relatively thin, in order to prevent the necessity of large, bulky, and/or uncomfortable material to accommodate pad 100. In an exemplary embodiment, pad 100 has a total thickness of no more than 10 mm.

Pad 100 provides several distinct advantages over conventional impact-resistant materials, as set forth below. The use of shear thickening fluid as fluid 120 desirably allows the pad to be thinner than conventional foam padding. Thinner pads are more comfortable for the wearer, which may be useful for sports equipment and/or medical devices. Additionally, the use of shear thickening fluid as fluid 120 desirably achieves a greater ability to resist the force of impacts than existing foams and gels currently used in conventional athletic equipment. Integrating shear thickening fluid into helmets, body pads, and other pieces of equipment may result in reduction of impact related injuries, like concussions and bruises. Still further, by using fluid 120, the weight of pad 100 desirably flows and moves with the wearer during use of pad 100. This may provide the user with a more comfortable and less rigid texture compared to conventional solid foam pads.

FIG. 2 illustrates an exemplary protective apparatus 200 in accordance with aspects of the present invention. Protective apparatus 200 may be configured to be worn by a participant during an athletic activity. As a general overview, protective apparatus 200 includes an impact-resistant pad 210. Impact-resistant pad 210 is a pad substantially as described above with respect to impact-resistant pad 100. Additional details of apparatus 200 are described herein.

Protective apparatus 200 is configured to protect a particular body region of the participant. For example, protective apparatus 200 may correspond in form to a traditional chest pad, leg pad, or helmet. Correspondingly, pad 210 has a shape that approximately conforms to an external periphery of the body region for which protective apparatus 200 is intended. For example, where protective apparatus 200 is a helmet, pad 210 may be shaped to surround a portion of the user's head (in order to effectively cushion impacts along that portion of the user's head). Similarly, where protective apparatus 200 is a leg pad, pad 210 may be shaped to surround a portion of the user's leg (in order to effective cushion impacts along that portion of the user's head). Suitable shapes and sizes of pad 210 will be dependent on the size of the user for which protective apparatus 200 is intended, and their selection will be understood on this basis by one of ordinary skill in the art.

As shown in FIGS. 2, apparatus 200 may also include one or more foam layers 220 and 230 provided on either side of pad 210. Foam layer 220 is positioned on a side of pad 210 that faces toward the participant when protective apparatus 200 is worn, and foam layer 230 is positioned on a side of pad 210 that faces away from the participant when protective apparatus 200 is worn. In an exemplary embodiment, foam layer 220 comprises a relatively softer foam than foam layer 230.

Pad 210 or foam layer 230 may be coupled to a frame 240 which is used to couple or secure protective apparatus 200 to the participant. In one embodiment, foam layer 230 is affixed to frame 240 with an adhesive. Alternatively, pad 210 may be affixed directly to frame 240 via the adhesive. Suitable frames for protective apparatus 200 will be known to one of ordinary skill in the art from the description herein.

The field-induced response of the shear thickening fluid in pad 210 can be engineered to yield optimal energy adsorption and impulse mitigation by tailoring their formulation for the specific application for which protective apparatus 200 is intended. Moreover, shear thickening fluids have the greatest potential to decrease the risk of impact related injuries if placed at the most statistically likely points of impact. For example, when protective apparatus 200 is a football helmet, it may be desirable to position pads 210 in the front and rear quadrants of the helmet, where the majority of hits are received.

FIG. 3 illustrates an exemplary method 300 for manufacturing an impact-resistant pad in accordance with aspects of the present invention. As a general overview, method 300 includes cutting the spacer fabric, creating the fluid, permeating the spacer fabric with the fluid, and encapsulating the spacer fabric and the fluid. Additional details of method 300 are described herein with respect to impact-resistant pad 100.

In step 310, the spacer fabric is cut into a desired shape and size. In an exemplary embodiment, a sheet of fabric is cut to form spacer fabric 110. The shape of spacer fabric 110 may be selected based on the desired shape and size of pad 100, as described above.

In step 320, fluid 120 is created. In an exemplary embodiment, a shear thickening fluid is created for use as fluid 120. The shear thickening fluid may be created by using a high shear mixer to mix approximately the first 40 wt % of silica nanoparticles with polyethylene glycol, and then using a roll mixer to disperse the remaining 15-21 wt % of silica nanoparticles in the polyethylene glycol. It may be desirable to allow the resulting fluid to roll mix for a number of hours to thoroughly mix the nanoparticles, and to degas the resulting mixture via conventional means (e.g., in a vacuum oven).

In step 330, the spacer fabric is permeated with the fluid. In an exemplary embodiment, spacer fabric 110 is permeated with fluid 120. In a preferred embodiment, spacer fabric 110 may be placed in a container full of fluid 120 and soaked until spacer fabric 110 is completed saturated with fluid 120 (e.g., via gravity-driven flow of fluid 120). Alternatively, spacer fabric 110 may be permeated with fluid 120 by passing spacer fabric 110 through a cascade of fluid 120, or via fluid injection or pumping of fluid 120 into spacer fabric 110.

In step 340, the spacer fabric and fluid are coated with a containment layer. In an exemplary embodiment, spacer fabric 110 and fluid 120 are encapsulated with containment layer 130. Containment layer 130 may comprise a polyolefin copolymer, as described above. To form containment layer 130, spacer fabric 110 and fluid 120 may be placed in a compression mold between a pair of sheets of polyolefin copolymer. Then, the sheets may be compressed and melted with the compression mold, in order to encapsulate spacer fabric 110 and fluid 120 therebetween. The compression mold may further be used to compress the resulting pad into the shape and structure desired for use.

EXAMPLES OF THE INVENTION

Exemplary impact-resistant pads are described below in accordance with aspects of the present invention.

Example 1

This example illustrates the reaction of an exemplary pad to the application of shear stress. As described above, the exemplary pad includes a shear thickening fluid to provide impact resistance. The shear thickening fluid (STF) used for this example was composed of 61% (by weight) NANOSIL® silica particles suspended in 200 g/mol polyethylene glycol (PEG). FIG. 4 shows shear stress vs. viscosity for the exemplary pad.

As shown in FIG. 4, increasing the shear rate leads to large increases in the stress response of the material. Note that a standard, Newtonian fluid would show a linear relationship between stress and shear rate, whereas the STF shows a highly nonlinear response to the applied shear rate above the critical value for shear thickening. It is this high stress that increases dramatically with increasing rate of deformation that provides the beneficial field-response of STF containing nanocomposites. For this example, shear thinning was observed from 0.1 Pa to 31.6 Pa and the minimum viscosity was measured to be 8 Pa*s. Shear thickening occurs for stresses above the critical value of shear stress, where the viscosity increases approximately two orders of magnitude from 8 Pa*s at the critical value to 305 Pa*s at the highest shear stress tested. A small amount of hysteresis was observed between the forward and backward stress sweeps, between 100 and 1000 Pa. This will not significantly affect the shear thickening performance of the fluid. Importantly, the fluid can be sheared back and forth many times without any measurable change in performance.

Example 2

These exemplary pads are designed for body protection (e.g., hip, elbow, ribs), and are no greater than 10 mm in total thickness. Two different spacer fabrics were used to form these exemplary pads. Both fabrics were from Gehring Textiles, Inc. The style numbers are used herein to distinguish between the fabrics. The first spacer fabric is designated SHR 879, and is made from firm textured polyester and is 5.8 mm thick. The second spacer fabric is designated SHR 858, which is made from a softer, more flexible polyester, and has the same thickness as SHR 879. Each spacer fabric was saturated with shear thickening fluid and encapsulated in 1 and 2 mm sheets of ENGAGE® 8200, provided by Dow Chemical Co.

Experimental data is provided herein regarding the performance of the exemplary pads in resisting the force of various impacts. In the experimental data described below, the pads are identified by total thickness, spacer fabric, and fluid formulation. In some experiments, the exemplary pads were combined with conventional foam to make prototype football helmet padding.

The exemplary pads were compared to an existing product, trade named ZOOMBANG®, and provided by Impacts Innovative Products LLC, of Irwin, Pa., USA. ZOOMBANG® pads are currently used by professional football players and other athletes as supplemental body padding (arms, legs, chest, joints). The ZOOMBANG® pad is 6 mm thick, which is comparable to the thickness of the exemplary pads. The experimental results demonstrate that the exemplary pads are systematically better than the ZOOMBANG® pad at attenuating peak force and dissipating energy.

FIG. 5 shows force vs. displacement for three exemplary pads and the ZOOMBANG® pad for impacts with kinetic energy of 15 J. The fluid for all the pads in FIG. 5 was shear thickening fluid comprising 58% silica nanoparticles by weight in 200 g/mol polyethylene glycol. The 7 and 10 mm SHR 879 pads only differ in the thickness of the Engage 8200 encapsulating layer. FIG. 5 shows that the thicker encapsulation provides negligible improvement in performance. This figure also shows that the SHR 858 spacer fabric performs somewhat better than SHR 879 during impact. Additionally, each of the exemplary pads has peak force of approximately 3 to 4 kN, which is half of the peak force experiences by the ZOOMBANG® pad, which was 8.6 kN.

Curves like those shown in FIG. 5 were used to calculate the energy dissipated for impacts ranging from 1 to 30 J. The area under the force vs. displacement curve describes the energy dissipated by the padding material. FIG. 6 shows energy dissipation percentage vs. impact kinetic energy for the exemplary impact-resistant pads, the ZOOMBANG® pads, and conventional ethylene vinyl acetate (EVA) foam padding. The ZOOMBANG® pad has energy dissipation of 80% at kinetic energy of 5 J, but that falls below 60% as kinetic energy is increased up to 30 J. Similarly, the EVA foams dissipate energy well during low kinetic energy impacts but the dissipation falls as kinetic energy increases. The EVA foams were completely compressed for impacts above 15 J.

All of the exemplary pads of the present invention have energy dissipation between 80-85% for the low kinetic energy impacts. The energy dissipation for the pads shown in FIG. 6 increases with kinetic energy up to local maxima between 10 and 15 J. The pad with the SHR 858 spacer fabric displayed the highest energy dissipation, approaching 99% during peak performance. The spacer fabric deteriorated during repeated experimental impact tests, which accounts for the slight decrease in energy dissipation in the 20 to 30 J range. This is most likely caused by impacting a small area repeatedly, which is not experienced by padding in real world situations.

Example 3

In accordance with another aspect of the present invention, shear thickening fluid padding may be used to replace foam in sports and other protective helmets. Conventional football helmets (such as those provided by Riddell, Inc. of Des Plaines, Ill., USA) use a two layer foam pad for their helmets, as shown in FIG. 7. The layer closest to the player's head is the softer of the two while the layer closest to the helmet shell is firmer. The firm layer is approximately 20 mm thick and the softer layer is approximately 10 mm thick, making the entire assembly approximately 33 mm thick.

FIG. 8 shows an exemplary embodiment of the foam padding including the impact-resistant pads of the present invention. For the embodiment shown in FIG. 8, the 8-10 mm of the firmer foam was replaced with a 7-8 mm thick exemplary impact-resistant pad. The spacer fabric used for this pad was SHR 858, with 1 mm thick ENGAGE® sheets used as the containment layer, and a shear thickening fluid (STF) having 61% silica nanoparticles by weight in 200 g/mol polyethylene glycol.

FIGS. 9-13 show force vs. displacement for the conventional foam helmet padding (shown in FIG. 7) and the foam pad including the exemplary impact-resistant pad of the invention (shown in FIG. 8). Both pads had the same total thickness of 33 mm and fit in the plastic casing that attaches the foam to the polycarbonate shell inside the conventional football helmet. The addition of inventive impact-resistant pad boosts the peak force attenuation and energy dissipation for impacts above approximately 14 J. FIG. 9 shows that for impacts of 3 J, the conventional foam and the inventive combination are both effective at dissipating the energy of the impact, and achieve similar peak forces. However, as the kinetic energy is increased to 15 J, the combination of foam and the inventive impact-resistant pad begins to have lower peak force. The presence of the fluid in the impact-resistant pad also allows the pad to dissipate more of the impact energy, which may be seen qualitatively as a wider force vs. deflection curve. The peak forces continue to be lower for the combination pad up to kinetic energy of 30 J, which was the highest kinetic energy measured for these samples. For the 30 J impact, the conventional foam has a very narrow force vs. deflection curve showing that it does a relatively poor job of dissipating the energy of the impact. The combination pad clearly dissipates more energy at 30 J and has a peak force that is approximately half of that for the conventional foam.

Further testing has demonstrated that combination pads having larger thicknesses of the inventive impact-resistant pad (such as 22 mm of impact-resistant pad and 11 mm of foam, or 33 mm of impact-resistant pad) have provided even further impact-resistance when compared with conventional foam pads.

Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention. 

What is claimed:
 1. An impact-resistant pad comprising a spacer fabric; a fluid permeated within the spacer fabric; and a containment layer encapsulating the spacer fabric and the fluid, wherein the fluid has a viscosity dependent on a force applied to the pad.
 2. The impact-resistant pad of claim 1, wherein the spacer fabric has a three-dimensional shape corresponding to a shape of the pad.
 3. The impact-resistant pad of claim 1, wherein the spacer fabric is formed from an elastically deformable material.
 4. The impact-resistant pad of claim 1, wherein the spacer fabric comprises polyester.
 5. The impact-resistant pad of claim 1, wherein the fluid comprises a shear thickening fluid.
 6. The impact-resistant pad of claim 5, wherein the shear thickening fluid comprises silica nanoparticles and polyethylene glycol.
 7. The impact-resistant pad of claim 1, wherein the fluid completely saturates the spacer fabric.
 8. The impact-resistant pad of claim 1, wherein the containment layer comprises polyolefin.
 9. The impact-resistant pad of claim 1, wherein the pad has a thickness of no more than 10 mm.
 10. A protective apparatus configured to be worn by a human, the protective apparatus comprising the impact-resistant pad of claim
 1. 11. The protective apparatus of claim 9, wherein the protective apparatus is configured to be worn by a human participant during an athletic activity.
 12. The protective apparatus of claim 9, wherein the impact-resistant pad has a shape that approximately conforms to an external periphery of a body region of the human.
 13. A method for manufacturing an impact-resistant pad comprising: cutting a spacer fabric to a desired shape; providing a fluid having a viscosity dependent on a force applied to the pad; permeating the spacer fabric with the fluid; and encapsulating the spacer fabric and the fluid with a containment layer.
 14. The method of claim 13, wherein the providing step comprises: providing a shear thickening fluid.
 15. The method of claim 14, wherein the providing step comprises: mixing silica nanoparticles with polyethylene glycol.
 16. The method of claim 13, wherein the permeating step comprises: completely saturating the spacer fabric with the fluid.
 17. The method of claim 16, wherein the permeating step comprises: placing the spacer fabric in a container of the fluid until the spacer fabric is completely saturated.
 18. The method of claim 13, wherein the encapsulating step comprises: positioning the spacer fabric and the fluid in a compression mold between a pair of sheets for forming the containment layer; and melting the pair of sheets to form the containment layer.
 19. The method of claim 18, further comprising the step of: is compressing the impact-resistant pad into a desired shape with the compression mold. 